Underground Practical Course at TUBAF Himmelfahrt Fundgrube
2026-02-16
💡 Gravity reductions
\[ \Delta g_{B} = \Delta g + \delta g_{S} + \delta g_{G} + \delta g_{C} + \delta g_{T} \]
\(\Delta g\): relative gravity, drift-corrected
\(\Delta g_{B}\): reduced relative gravity
Further required for reductions:
Remove instrument drift taken at fixed point P0: \[ \Delta g(z) = g(z,t) - g_G(z_{0}, t), \]
The \(\Delta g(z)\) are the unreduced relative gravity data.
We now have to
💡 \(\rightarrow\) Gravity reductions
At P2 a cavity (Radstube) is right below the gravity meter. The missing rock mass has to be added to the plate model.
The terrain above the shaft is not flat. We approximate the piling by a rectangular prism of the same volume.
We use Python to calculate the gravity effect of a rectangular 3-D prism.
Code is available at GitHub repository.
| Interval | \(\Delta g_{2}\) [mGal] | \(\Delta g_{1}\) [mGal] | \(z_2 - z_1\) [m] | \(g_h\) [mGal/m] | \(\rho_B\) [kg/m³] |
|---|---|---|---|---|---|
| P0–P1 | |||||
| P1–P2 | |||||
| P2–P3 | |||||
| P0–P3 |
Python code, PDF’s, etc. are at https://github.com/TUBAF-EM/MineShaft_Geophysics